For the surgical repair and stabilization of fractures of long bones, such as femur, tibia, humerus and fibula, it has long been known in medical practice to insert an intramedullary nail, which is a tubular metal part, of appropriate length into the interior portion of the bone. The nail usually has a pair of transverse holes adjacent to its proximal end (proximal holes) and a pair of transverse holes adjacent to its distal end (distal holes). In order to enhance the healing of the bone, the nail must provide a rigid structure about which the broken portions of the bone may adhere. Thus, the nail must be secured with respect to the bone. The securing of the nail is achieved by means of transversely extending screws or bolts which are screwed into the bone and pass through the surrounding tissue and through the transverse holes.
The procedure for inserting the screws requires: (a) accurate location of the transverse holes in the nail; (b) drilling screw holes in precise alignment with the transverse holes and preventing the drill from touching the nail; (c) inserting the screws into the drilled holes and through the transverse holes so as to secure the nail with respect to the bone.
The problem has always been that once the nail is inserted into the bone, the transverse holes are said to be “blind” in the terms of the bone-drilling alignment that must be achieved. Therefore, the most critical part of this procedure is to determine from outside the location, particularly the center, and the axis of these holes.
For this purpose, it is known to use a jig including a frame and different positioning means, by means of which approximate locations of the holes are determined before the nail is inserted into the bone. For proximal holes the problem is solved by means of such a jig relatively simply, since the proximal holes are adjacent to the area of the attachment of the frame of the jig and their location with respect to the proximal end of the nail almost doesn't differ from the location determined before the nail was inserted into the bone.
The determination of the location of the distal holes is much more difficult, due to the fact that the nail may have undergone a slight bent or twisting during the insertion thereof into the bone, so that the distal holes no longer have the same location with respect to the proximal end of the nail, as it was prior to its insertion.
Due to the above mentions limitations, majority of techniques have to rely on X-rays for assurance of the alignment. C-arm is often used for this purpose, since it allows directional control of the X-ray beam. One of the most common techniques using C-arm is a so-called “free hand technique”. This technique depends heavily on the experience and steady hand of the surgeon. Moreover, the technique involves a great radiation exposure of the surgeon while working with hands close to the X-ray beam.
Several approaches have been used to determine the location of the transverse holes. U.S. Pat. Nos. 4,803,976; 5,411,503; 6,129,729; 6,635,061 and 6,656,189 disclose examples of different sighting and aiming jigs. U.S. Pat. No. 5,433,720 have proposed magnetic detection for location of a central axis of the holes. U.S. Pat. Nos. 4,865,025; 6,207,506 and 6,039,742 disclose several methods for locating the holes using all-mechanical devices. WO 03/105659 discloses a robot guided system comprising a miniature robot holding a targeting drill guide, which is automatically positioned by the robot relative to the distal holes. Finally, U.S. Pat. Nos. 5,540,691 and 5,417,688 disclose an optical system and method for locating the distal holes using a light source positioned adjacent to the holes.